In the teaser trailer we see that the anime will be, at least partially, set in North Ambria and centers around the Northern Jaegers, which are both very important to the Cold Steel narrative. The new character introduced in the trailer is Lavi, a Northern Jaeger and the granddaughter of a hero of North Ambria who seemingly abandoned it. She is tasked with infiltrating the Erebonian Empire and gaining intelligence on their “hero” the seemingly threatens everyone. Other new characters introduced are Talion, Iseria, Marty. The teaser ends with a broadcast date of 2023.
In the second trailer we learn that Lavi in an instructor of some kind and had been promoted at the age of 15. It is also heavily implied the North Ambria will be consumed in conflict if the Hero of the Empire is allowed to do as he, or the Empire, pleases.
Mild spoilers for anyone who has not played at least the first two entries in the Trails of Cold Steel series………………………………………………………………………………………………………………
This anime seems to take place after Trails of Cold Steel II as Rean has command of Valimar and is working as an agent of the Erebonian Empire following its civil war and during its annexation of the rest of the Zemurian continent under The Blood and Iron Chancellor Giliath Osborne.